US4163520A - Electrostatic liquid spraying nozzle - Google Patents

Electrostatic liquid spraying nozzle Download PDF

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Publication number
US4163520A
US4163520A US05/906,761 US90676178A US4163520A US 4163520 A US4163520 A US 4163520A US 90676178 A US90676178 A US 90676178A US 4163520 A US4163520 A US 4163520A
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US
United States
Prior art keywords
electrode
nozzle
downstream end
liquid
outlet
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US05/906,761
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English (en)
Inventor
Felix Garcin
Marcel Weil
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Air Industrie SA
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Air Industrie SA
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Publication date
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
    • B05B5/025—Discharge apparatus, e.g. electrostatic spray guns
    • B05B5/03—Discharge apparatus, e.g. electrostatic spray guns characterised by the use of gas, e.g. electrostatically assisted pneumatic spraying
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/02—Spray pistols; Apparatus for discharge
    • B05B7/06—Spray pistols; Apparatus for discharge with at least one outlet orifice surrounding another approximately in the same plane
    • B05B7/062—Spray pistols; Apparatus for discharge with at least one outlet orifice surrounding another approximately in the same plane with only one liquid outlet and at least one gas outlet
    • B05B7/066—Spray pistols; Apparatus for discharge with at least one outlet orifice surrounding another approximately in the same plane with only one liquid outlet and at least one gas outlet with an inner liquid outlet surrounded by at least one annular gas outlet
    • B05B7/067—Spray pistols; Apparatus for discharge with at least one outlet orifice surrounding another approximately in the same plane with only one liquid outlet and at least one gas outlet with an inner liquid outlet surrounded by at least one annular gas outlet the liquid outlet being annular

Definitions

  • the present invention relates to an air-assisted electrostatic round-spray nozzle intended to spray liquid products, for instance paints or enamels.
  • Such nozzles are well-known by the man of the art and equip, or have equipped, certain types of manual guns of the applicant, such as, for example, the guns sold at present under the reference “Statair MRV 66" or sold formerly under the reference “Statair K”.
  • Statair MRV 66 the guns sold at present under the reference "Statair MRV 66" or sold formerly under the reference "Statair K".
  • They are either described or represented in numerous publications, such as, for example the French patents published under Pat. Nos. 1,358,199, 1,366,864, 1,394,834, 1,537,997, 2,050,317, 2,052,003, 2,053,425, 2,102,675, 2,115,663, 2,120,393.
  • They comprise:
  • At least one charging electrode made of electrically conductive material, brought to high voltage and generally located at the downstream end of the nozzle;
  • a "diffuser" intended to shape the incident stream of liquid, before atomization, into a liquid thin-walled tube, or tubular film. It is only in fact due to this shaping into a thin tubular film of large diameter that it is possible to obtain, with a round-spray nozzle, satisfactory spraying with industrially acceptable flow rates of paint and air;
  • At least one atomizing gas outlet is generally a ring-shaped space surrounding the downstream end of the insert, and giving a swirling spray according to French Pat. No. 1,366,864.
  • a nozzle is placed at the end of an electrostatic spray-gun.
  • Such a resistor has the effect of regulating the field between the nozzle and the object when their distance varies, and provides in addition appreciable protection against accidental discharges from the capacity of the cable connecting the gun to the high voltage generator, discharges which would give rise to violent sparks liable to cause a fire.
  • the air-assisted electrostatic round-spray nozzle according to the invention makes it possible to obtain a discharge energy, measured when no spraying is taking place, which is distinctly reduced in comparison with that of the nozzles with end metal electrode(s) existing at present. It is characterized in that, except for the said charging electrode(s), the diffuser, the insert, together with the whole of the outer part of the nozzle, are made of electrically insulating material, and in that the said electrode(s) are formed by one or more points or pin-point zones located substantially in the atomization plane and inside the liquid thin-walled tube formed in the space between the insert and the diffuser.
  • atomization plane is meant the plane through which the liquid passes--or begins to pass--from the continuous liquid phase to the discontinuous phase, i.e. to transformation into droplets. In practice, with a round-spray nozzle, this plane is generally the front side of the nozzle, or very slightly in front of the said front side.
  • substantially in the atomization plane is meant preferentially in the atomization plane, but without excluding a very slight displacement forwards or backwards from the plane; the said displacement may be a fraction of a millimeter, or even a millimeter, while still remaining within the scope of the invention: the atomization plane may not, in fact, be fixed to the exact millimeter.
  • pin-point zone is meant a zone of very small diameter, and in any case hardly bigger than a pin-head.
  • FIG. 1 shows diagrammatically a manual electrostatic round-spray paint gun, equipped with a nozzle according to the invention
  • FIG. 2 shows an enlarged view of the nozzle equipping the gun of FIG. 1.
  • numeral (1) refers to a manual electrostatic paint-gun strictly identical, apart from its nozzle which is the subject of the invention, to the round-spray guns at present sold by the applicant under the reference MRV 66. It has, as known per se, a hand grip (2), a trigger (3), an insulating barrel (4) and an atomizing nozzle (5).
  • the paint and compressed air intakes, as also the high voltage cable, have not been shown on the drawing, being conventional.
  • downstream end (6) of the high voltage cable may be distinguished, however, the downstream end (6) of the high voltage cable, as also the high value resistor (7), for example a hundred or so megohms with a high voltage of 60 kilovolts, embedded in the barrel (4) of the gun, in series between the inlet (6) of the high voltage cable and the metal charging electrode (8) placed at the end of the gun.
  • the high value resistor (7) for example a hundred or so megohms with a high voltage of 60 kilovolts, embedded in the barrel (4) of the gun, in series between the inlet (6) of the high voltage cable and the metal charging electrode (8) placed at the end of the gun.
  • FIG. 2 where there is an enlarged view of the downstream end of the gun (1) equipped with the nozzle (5) according to the invention screwed on to the end of the barrel (4), there may be recognized:
  • a circuit bringing the paint comprising:
  • transition tube (16) bringing the paint towards the injector (32) properly speaking, formed by an insert (17) and a diffuser (18) leaving between them a thin ring-shaped space (19) necessary for creating the thin tubular film of paint which is to be atomized by the stream of compressed air.
  • All these parts are made of insulating material, except part (15) and except the pin (12) formed by a metal end (20) fixed into an insulating rod (21).
  • annular chamber (22) with, as known per se, tangential air intakes (33) and direct air intakes (23);
  • an atomization air outlet ring (24), narrowly surrounding the downstream end of the paint injector (32).
  • a metal spring (29) ensuring the electrical connection between the seating (15) of the pin and a fine metal wire (30) crossing axially, through and through, the insulating diffuser (18) and ending up, according to the invention, exactly in the downstream plane (31) of the diffuser (18), so as to create there a pin-point electrode (8).
  • the strictly axial position of the pin-point electrode (8) is preferred for several reasons: it is first of all advantageous to be entirely symetric on all sides from the point of view of protection against sparks: in this way, distance from the electrode (8) is always the same, however the painter brings the gun near the earthed object. If, for example, the pin-point electrode (8) was displaced upwards, a spark of low energy would in fact be obtained when an earthed object is approached from above, but on the contrary a spark of stronger energy would be obtained when an earthed object is approached from underneath, as explained previously. It is therefore preferable, through not absolutely compulsory so long as the electrode remains within the ring delimiting the front side (31) of the diffuser, i.e. within the annular tube of paint (19), to place said electrode (8) exactly in the axis of the nozzle.
  • the front side (31) of the diffuser (18) is, when operating, permanently covered by capillarity with a film of paint forming a continuous link with the tubular film (19).
  • the electrode (8) of the invention is thus covered by this film, so that the electric charging of the paint takes place by conduction through it, which is generally more effective than charging by bombardment according to the devices of French Pat. No. 1,285,345; here again, the electric charge of the paint will be distributed more symetrically if the electrode (8) is axial and not off the axis.
  • the electrode (8) of the invention is inside the annular film of paint (19), i.e. to be situated on the front side (31) of the diffuser (18) itself; otherwise, there could obviously be no charging by conduction, and, on the other hand, the man of the art is well aware that pin-point electrodes placed outside the ring of paint tend, no doubt on account of the parasitic concentration of lines of force they produce, to cause dirty marks both on the nozzle, gun and painter, and tend furthermore to perturb, for the same reasons, the electrostatic charging of the paint.
  • pin-point electrode (8) Only one pin-point electrode (8) has been shown on the drawing, for this corresponds to the simplest construction and is thus to be preferred. It is evidently likewise possible to have several pin-point electrodes placed in the downstream plane (31) of the diffuser (18), while still remaining in the scope of the invention.
  • the applicant has produced an electrode formed by a star-shaped cluster of points situated in plane (31): for this, wire (30) was replaced by an electrical wire formed by a score of wires of very small diameter being twisted together.
  • the so-formed wire was made to project 2 millimeters beyond the plane (31); then the said projecting part was crushed into a star shape, so as to obtain a cluster of fine needles situated within the said plane: the results obtained both in spark tests and in electrostatic spraying were not appreciably different from those obtained in the preferential construction described with reference to FIGS. 1 and 2.
  • the nozzle according to the invention may be used on all types of electrostatic liquid spraying guns, either manual or automatic. It is used most advantageously in the electrostatic paint and enamelling industry.

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  • Electrostatic Spraying Apparatus (AREA)
US05/906,761 1975-07-29 1978-05-16 Electrostatic liquid spraying nozzle Expired - Lifetime US4163520A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH984875A CH598871A5 (en)) 1975-07-29 1975-07-29

Related Parent Applications (1)

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US05702422 Continuation 1976-07-06

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US4163520A true US4163520A (en) 1979-08-07

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US05/906,761 Expired - Lifetime US4163520A (en) 1975-07-29 1978-05-16 Electrostatic liquid spraying nozzle

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US (1) US4163520A (en))
JP (1) JPS5216546A (en))
CH (1) CH598871A5 (en))
DE (1) DE2633687A1 (en))
FR (1) FR2319425A1 (en))

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4341347A (en) * 1980-05-05 1982-07-27 S. C. Johnson & Son, Inc. Electrostatic spraying of liquids
USRE31867E (en) * 1978-02-13 1985-04-16 Nordson Corporation Electrostatic spray gun
DE3412266A1 (de) * 1984-04-02 1985-10-03 J. Wagner AG, Altstätten Elektrostatische farbspritzpistole
US4548363A (en) * 1983-09-06 1985-10-22 Pcf Group, Inc. Muzzle for electrostatic spray gun
AU580147B2 (en) * 1985-04-18 1989-01-05 Nordson Corporation Particle spray gun
US4819879A (en) * 1985-10-25 1989-04-11 Nordson Corporation Particle spray gun
US5078325A (en) * 1990-09-18 1992-01-07 Nordson Corporation Coating dispenser with removable valve tip and valve seat
US5261610A (en) * 1990-09-18 1993-11-16 Nordson Corporation Coating dispenser with hydraulic-assisted valve closure
US20160368008A1 (en) * 2015-01-12 2016-12-22 Ben-Why Liao Spray head structure slidably assembled with a nut

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4182490A (en) * 1978-02-13 1980-01-08 Nordson Corporation Electrostatic spray gun
GB9012307D0 (en) * 1990-06-01 1990-07-18 Ingredients Limited Ab Electrostatic spray apparatus
FR2706329B1 (fr) * 1993-06-15 1995-08-25 Sames Sa Pulvérisateur pneumatique de produit de revêtement à jet plat.
DE19646277A1 (de) 1996-11-09 1998-05-14 Itw Oberflaechentechnik Gmbh Sprühbeschichtungseinrichtung

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3233831A (en) * 1962-06-04 1966-02-08 Sames Mach Electrostat Electrostatic spraying apparatus having vortex atomizing construction
US3795839A (en) * 1967-09-01 1974-03-05 Graco Inc Method for preventing arcing in an electrostatic coating system

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1408758A (fr) * 1964-06-23 1965-08-20 Sames Mach Electrostat Perfectionnements aux procédés de recouvrement d'objets, et moyens pour leur mise en oeuvre
FR1578913A (en)) * 1968-05-03 1969-08-22

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3233831A (en) * 1962-06-04 1966-02-08 Sames Mach Electrostat Electrostatic spraying apparatus having vortex atomizing construction
US3795839A (en) * 1967-09-01 1974-03-05 Graco Inc Method for preventing arcing in an electrostatic coating system

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USRE31867E (en) * 1978-02-13 1985-04-16 Nordson Corporation Electrostatic spray gun
US4341347A (en) * 1980-05-05 1982-07-27 S. C. Johnson & Son, Inc. Electrostatic spraying of liquids
US4548363A (en) * 1983-09-06 1985-10-22 Pcf Group, Inc. Muzzle for electrostatic spray gun
DE3412266A1 (de) * 1984-04-02 1985-10-03 J. Wagner AG, Altstätten Elektrostatische farbspritzpistole
EP0157200A3 (en) * 1984-04-02 1986-10-08 Wagner International Ag Electrostatic paint spraygun
US4651932A (en) * 1984-04-02 1987-03-24 J. Wagner Ag Electrostatic paint spraygun
AU580147B2 (en) * 1985-04-18 1989-01-05 Nordson Corporation Particle spray gun
US4819879A (en) * 1985-10-25 1989-04-11 Nordson Corporation Particle spray gun
US5078325A (en) * 1990-09-18 1992-01-07 Nordson Corporation Coating dispenser with removable valve tip and valve seat
US5261610A (en) * 1990-09-18 1993-11-16 Nordson Corporation Coating dispenser with hydraulic-assisted valve closure
US20160368008A1 (en) * 2015-01-12 2016-12-22 Ben-Why Liao Spray head structure slidably assembled with a nut

Also Published As

Publication number Publication date
JPS5216546A (en) 1977-02-07
CH598871A5 (en)) 1978-05-12
DE2633687A1 (de) 1977-02-03
FR2319425A1 (fr) 1977-02-25
FR2319425B1 (en)) 1978-09-01

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